Include attributes.h directly

Some files currently rely on libavutil/cpu.h to include it for them;
yet said file won't use include it any more after the currently
deprecated functions are removed, so include attributes.h directly.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavutil/mips/libm_mips.h

@@ -53,6 +53,8 @@
 #ifndef AVUTIL_MIPS_LIBM_MIPS_H
 #define AVUTIL_MIPS_LIBM_MIPS_H
 
+#include "libavutil/attributes.h"
+
 static av_always_inline av_const long int lrintf_mips(float x)
 {
     register int ret_int;